Pension and postretirement benefits - Components of Plan Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 30, 2024	Oct. 01, 2023
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 0
Interest cost	7
Expected return on plan assets	(9)
Amortization of unrecognized prior service cost	1
Total pension expense	1
Nonpension postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	$ 0
Interest cost	6
Expected return on plan assets	(15)
Amortization of unrecognized prior service cost	(2)
Total pension expense	$ (10)